Hello Everyone,
please what should be the ideal working concentration of mercury in Order to get a better results from ICP- MS. Should it be in ppm or ppb? Or it should be based on the limit of detection of mercury which is 2 ppb? Thank you
Hi there
Mercury is difficult to analyse in any instrument for few reasons
Mercury is "sticky"
This means many things such as:
- If you use high concentration standards ppm, chances are all your system will get mercury contamination in tubing, spray chamber, nebuliser, etc . This will eventually increase the Mercury background, therefore also increasing the detection limits.
- It also means that for example if you attempt to prepare low concentration calibration standards (few ppb), then even in plastic and more so in glassware, such low amount of mercury will get stuck into the container. You will then need to always prepare fresh calibration standards. It also raises questions about the concentration in your sample as such concentration (with no pretreatment)
So regardless of how difficult Mercury is to analyse you can follow the following practices:
Knowing that Mercury loves to bin with sulfur, you can use that to your advantage.
Instead of rinsing with high concentration acids (10% aqua regia, 10% nitric /hydrochloric acid) it is better to rinse with a sulfur containing solution such as 1% cysteine, mercaptoethanol, etc in 1% acid). In this way Mercury remains as a very soluble complex (also perhaps more dangerous as it is more mobile).
Same applies to your samples and standards at low concentrations (but how do you know samples are low concentrations in the first place?) you can add cysteine to stabilise.
I hope this helps
Leonardo Pantoja Munoz , does that mean I can prepare the working concentrations to be say 20 and 10 ppb!!
Hi.
Yes as long as you rinse, prepare your standards and pretreat samples with 1% cysteine or mercaptoethanol in 1% acid.
Some people use gold to stabilise mercury, but I dont like it because my background of gold increases so much that i dont get ppt detection limits when i do gold analysis
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